Biodiesel can be used in modern diesel engines in pure form or may be blended with petroleum diesel (petro-diesel) at any concentration.
It has to be noted that the biodiesel blending level is commonly expressed by means of the biodiesel percentage with respect to the petro-diesel. Usually the expression Bxx is used to indicate the biodiesel blending level, wherein the term “xx” is the biodiesel percentage with respect to the petro-diesel. In other words, a biodiesel blend with 30% of biodiesel is indicated as B30. Obviously, B0 is petro-diesel, while B100 indicates a biodiesel fuel without petro-diesel.
Using biodiesel may have positive effects such as particulate reduction, possibility of reduction of the regeneration frequency of the diesel particulate filter (DPF), etc., and also negative effects such as increased nitrogen oxides emission and increased oil dilution.
Both positive and negative effects deriving from the use of a biodiesel are strictly related to the amount of biodiesel into the fuel, i.e. the biodiesel percentage with respect to the petro-diesel. For example, the higher distillation curve of the biodiesel reduces the amount of the fuel that evaporates, and for this reason the amount of the biodiesel in liquid phase injected into the cylinder increases enormously.
The higher amount of biodiesel in liquid phase into the cylinder causes the passage into the cylinder liner, which leads to an increasing of the oil dilution. As verified by the applicant by means of experimental tests, i.e. run at 2000×5 [rpm×bmep] which consist of 20 repeated complete regeneration cycles, with a 5% of biodiesel (B05) the fuel dilution in oil is roughly 0.3% of the total oil mass per regeneration cycle. With 100% of biodiesel (B100) the fuel dilution in oil is roughly 1% of the total oil mass per regeneration cycle.
For these and other reasons there is the need to determine the actual biodiesel percentage that expresses the biodiesel blending.
The pending patent applications GB0918272.6 and GB0918273.4, in the name of GM Global Technology Operations Inc., disclose two methods for detecting the biodiesel blending respectively based on the evaluation of the mean effective pressure and of the relative air-to-fuel ratio.
It is at least one object herein to provide an alternative method for detecting the biodiesel percentage into the fuel that expresses the biodiesel blending level. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.